The present invention relates to a technique suitable to safely verify only a qualification and/or a privilege without giving information identifying an individual and a device contained in a public key certificate to a verifier.
In services provided on a network, there is employed an authentication method using a public key certificate to identify a communication partner. In this regard, a method using an attribute certificate is known as the method of verifying a qualification and a privilege with safety at a public key cryptography level. For example, reference is to be made to “Information technology—Open systems interconnection—The Directory: Public-key and attribute certificate frameworks (ITU-T Recommendation X.509)” published from International Telecommunication Union, (Switzerland) on Mar. 31, 2000. The public key certificate is data in which a value of a public key is linked with a name, an identification number of a device, or the like of a subject possessing a private key corresponding to the public key, and the contents thereof are guaranteed by a digital signature of a certification authority.
The attribute certificate is data in which information identifying a public key certificate is linked with attribute information possessed by a subject of the public key certificate, and contents thereof are guaranteed by a digital signature of an attribute authority. In this connection, the information identifying a public key certificate generally includes an issuer name and a serial number of the public key certificate and does not include information individually identifying the subject of the public key certificate such as identification information identifying a name and a device of the subject of the public key certificate.
Moreover, to verify a qualification using an attribute certificate, there are employed in addition to the attribute certificate a digital signature of a holder of the attribute certificate and a public key certificate corresponding to the attribute certificate as well as a public key certificate constituting a certification path from a certificate of a certification authority trusted by the holder to the attribute certificate and the public key certificate and revocation information about each certificate in the certification path.
The methods to efficiently verify an attribute certificate includes a method in which a verifier transmits an attribute certificate to be verified and a public key certificate of a trusted certification authority to an attribute certificate validation device and the validation device delegates validation processing to return a result thereof to the verifier. For example, reference is to be made to JP-A-2003-348077.